Many people believe that glaucoma, also known as glaucoma, is associated with increased intraocular pressure. But this is a misconception: often the intraocular pressure is within the normal range – but the optic nerve is still at risk. Anyone who, as a result of this misconception, independently forgoes the prescribed antiglaucoma medication, i.e. the eye drops against glaucoma, because he believes his intraocular pressure to be within the normal range, risks the death of the optic nerve cells and thus an irreversible loss of vision. We explain the connections.
What intraocular pressure is normal?
For intraocular pressure, normal values range from 10 to 21 mmHg (millimeters of mercury). Thereby, the values of the intraocular pressure fluctuate in the course of a day by approximately 5 mmgH. Especially at night and early in the morning the values can be higher than usual. The values can also be higher in older people, and 10 to 12 mmHg is considered normal in children.
Increased pressure in the eye, i.e. 22 mmHg and above, is considered a risk factor for the development of glaucoma – although this does not necessarily have to occur. Conversely, the intraocular pressure does not have to be elevated to develop glaucoma (normal pressure glaucoma).
The intraocular pressure is measured with the help of a so-called applanation tonometer. This device measures the pressure needed to deform a specific area of the cornea.
Examine the optic nerve with
Prof. Lutz E. Pillunat, clinic director of the University Eye Hospital in Dresden and a member of the Professional Association of Ophthalmologists, is familiar with the misconceptions surrounding the diagnosis of glaucoma: “It is a fatal and unfortunately still widespread misconception that glaucoma is fundamentally associated with increased intraocular pressure.”
In many glaucomas, the pressure values are in the normal range and yet the optic nerve is threatened. Therefore, glaucoma screening makes sense only if the condition of the optic nerve is assessed at the same time as intraocular pressure measurement.
Normal-tension glaucoma: causes
“For glaucoma without a noticeably high intraocular pressure, various reasons come into question: a low tolerance limit – here, even a relatively low pressure destroys the sensitive nerve fiber cells,” says Prof. Pillunat. At the same time, the blood supply to the optic nerve may be disturbed – it is not sufficiently supplied with oxygen and nutrients. Misregulation of the vascular system is characteristic of normal-pressure glaucoma.
Eye drops to prevent glaucoma.
Another misconception is that glaucoma medications merely lower intraocular pressure. Many eye drops prescribed today additionally improve blood flow to the retina and optic nerve.
“As a result of ignorance and misconceptions, glaucoma is still one of the most common causes of blindness – despite reliable diagnostic methods and effective therapeutic concepts that can preserve vision,” explains Prof. Pillunat.
Early detection leads to the best therapy
To ensure that glaucoma can be detected and treated before damage occurs to the optic nerve, everyone from the age of 40 should take advantage of the ophthalmologic examination for early glaucoma detection every two years as a precaution. This consists of a combination of an examination of the optic nerve and an intraocular pressure measurement.
If glaucoma is known to run in the family, it is advisable to have the screening examination from the age of 35 and annually. Closer screening is also advisable for people with diabetes.
If glaucoma has been diagnosed, it is essential that the patient conscientiously follows the therapy prescribed by the ophthalmologist.
The public health insurances do not take over the screening examination, nevertheless one should absolutely treat oneself to the small costs into its eyesight.
